In the past, surfboards had fins mounted and fixed at the rear portion of the board. The trend, however, has been to design a fin that can be adjusted along the length of a channel on the underside of the board. The adjustable feature has become important, because surfers have found that placement of the fin affects an individual's control of the board. Also, it is desirable to have the adjustment capability for varying surf and weather conditions as well as for the individual's preference.
Some adjustable fin systems in the past have relied on the use of screws or moving plates, or other mechanical locking devices to adjust the fin relative to the length of the board. This arrangement requires the surfer to have access to tools such as a screwdriver or wrenches to make a longitudinal adjustment to fasten the fin. This is a limitation on how and when the surfer can adjust the fin. In addition, the necessary mechanical parts for adjusting the fin are subject to corrosion in the salt water environment. In some cases the screw clamps or plates extend beneath the surface of the board creating the possibility of drag on the board.
Other adjustable fin arrangements have avoided the use of tools for the adjustment and substituted complex systems of wedges, keying elements, tabs and flanges as exemplified in U.S. Pat. No. 3,585,663 to Johnson issued June 22, 1971. This more complicated construction does not facilitate manufacturing. Also, some of the fin arrangements, such as on the Johnson patent, have a restricted number of positions along the undersurface of the board for securing the fin, thereby limiting the surfer in the degree of flexibility of longitudinal fin adjustment.
In addition to the adjustability of the fin for the benefit of use of the board, the removable feature of the fin aids in shipping and storage of the surfing equipment. The fin and board can be shipped separately and assembled later. This also gives the surfer the option to use different shapes and sizes of fins.